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# M3 - edexcel - Elastic strings and springs watch

1. I am attaching the question I'm trying to do. I have done parts a) and b) but c) has me stumped. The solutions says that the least force required will be perpendicular to the string. Why is that and is it something I should have known?

Thanks
Attached Files
2. Doc1.doc (238.0 KB, 55 views)
3. (Original post by maggiehodgson)
I am attaching the question I'm trying to do. I have done parts a) and b) but c) has me stumped. The solutions says that the least force required will be perpendicular to the string. Why is that and is it something I should have known?

Thanks
Three forces in equilibrium - use the triangle of forces.

You know the weight, you know the direction of the tension. The third force will be minimum, i.e. shortest length to the tension force, when it's perpendicular to the line representing the tension.

Draw the diagram, if you're still unsure.
4. (Original post by ghostwalker)
Three forces in equilibrium - use the triangle of forces.

You know the weight, you know the direction of the tension. The third force will be minimum, i.e. shortest length to the tension force, when it's perpendicular to the line representing the tension.

Draw the diagram, if you're still unsure.
Thanks

If I ever knew that then I'd forgotten. If looked at Triangle of Forces on the web and it does make sense.

Many thanks

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